Communication Product Updates

Below are brief descriptions of communications products recently developed by the Federal Highway Administration’s (FHWA) Office of Research, Development, and Technology. All of the reports are or will soon be available from the National Technical Information Service (NTIS). In some cases, limited copies of the communications products are available from FHWA’s Research and Technology (R&T) Product Distribution Center (PDC).

When ordering from NTIS, include the NTIS publication number (PB number) and the publication title. You also may visit the NTIS Web site at www.ntis.gov to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:

Field Evaluation of a Restricted
Crossing U-Turn Intersection (Report)

Publication Number: FHWA-HRT-11-067

In rural areas, left turns and through movements onto or
across four-lane divided access highways too often result in serious crashes.
The restricted crossing U-turn intersection design is intended to address this
safety issue. This report highlights the results of a study involving
observations of driver performance at such an intersection in Maryland. The
report also summarizes the results of an empirical Bayes crash analysis
performed for intersections along two Maryland corridors before and after
conversion to a restricted crossing U-turn.

The observation portion of the study was intended to support
design guidance for future designs of restricted crossing U-turns. The
researchers focused on the differences between conventional and restricted
crossing U-turn intersections in the following areas: conflicts between
vehicles, merging behaviors, lag acceptance, weaving, and travel times. They
performed crash analyses to examine the effects of converting intersections
from conventional to restricted crossing U-turns along two rural high-speed
divided highway corridors. These analyses focused on nine restricted crossing
U-turn intersections built between 1998 and 2003.

Researchers used three methods of analysis and ultimately
determined that the restricted crossing U-turn design reduced crashes between
28 and 44 percent. The crash data suggest that the overall severity of crashes
is lower with the restricted crossing U-turn design than at conventional
stop-controlled intersections. Researchers observed a 70 percent reduction in
fatal crashes and a 42 percent reduction in crashes that resulted in injuries.

Further, the researchers concluded that the restricted
crossing U-turn design should be considered for minor road intersections with
four-lane divided highways where there is a sufficient volume of traffic on the
minor road. The design greatly reduces the probability of angle crashes at the
cost of a minimal increase in travel time. As volume on the divided highway
increases, the travel time penalty is likely to decline, and the safety benefit
is likely to increase.

To realize its potential in the 21st century,
the concrete paving industry has identified trends that call for dramatic improvements.
FHWA and its industry partners are looking to implement these improvements
through a holistic approach and using a carefully developed and aggressively
implemented strategic plan for research and technology transfer. The Long-Term Plan for Concrete Pavement Research and Technology,
also known as the Concrete Pavement (CP) Road Map, tracks and facilitates
technologies that will help the concrete pavement community meet current and
future needs.

This report is the second of two volumes. The first addresses the need for the CP Road Map and describes its
background and development, critical issues and objectives, and a research
management plan. The second details the 12
tracks of planned and ongoing research, with more than 270 research problem
statements grouped into the tracks. Each track begins with introductory
material that summarizes the objectives for the track and the gaps and
challenges for its research program. A table of estimated costs provides the
projected cost range for each problem statement, which depends on research
priorities and the scope determined in implementation.

The 12 tracks are expected to lead to specific products that
will change the way concrete pavements are designed and constructed.
Ultimately, FHWA and its partners intend the CP Road Map to help move new and
useful products and systems quickly and efficiently into practice.

Ride quality and structural adequacy are key indicators
of pavement performance, but how do they relate to each other? This TechBrief
presents major findings and conclusions from a study sponsored by FHWA to
determine the relationship between these indicators using data from the
Long-Term Pavement Performance program.

Researchers generated continuous plots for International
Roughness Index, effective pavement structural number for flexible pavements,
and effective concrete slab thickness for rigid pavements. They did not observe
a viable relationship between the two parameters in the sections and data
investigated.

The researchers' discovery of a lack of correlation could be
of value to pavement management system practitioners, as it indicates that good
ride quality does not mean good structural adequacy or vice versa. This is an
important consideration for those who want to base performance measures on ride
quality indicators. Although pavement functional and structural performances
are not independent of each other, they are not related in a one-to-one manner
that can easily be implemented within a pavement management system. A strong
relationship between these two performance indicators would likely require the
inclusion of many other variables, limiting its usefulness.

Transverse rumble strips are designed to provide drivers
with a tactile and audible warning signal to slow down. Although some
crash-based studies have shown that rumble strips are effective in reducing
intersection approach speeds, the results from these studies are not reliable
when examining crash data. This summary report highlights a study of rumble
strips on approaches to stop-controlled intersections in rural areas. It
details the impact of transverse rumble strips on total crashes, injury crashes,
and specific crash types, such as right-angle and run-STOP-sign crashes.

The study investigated the safety effect of transverse rumble
strips on approaches to stop-controlled intersections using an empirical Bayes
methodology. Results indicate that rumble strips may be effective in reducing
severe injury crashes at stop-controlled intersections on minor roads. However,
the researchers noted an increase in crashes involving property damage only.
Although they could not definitively state the reasons for this tradeoff, a
limited economic analysis indicated a reduction in crash harm of about $6,600
per intersection per year due to the installation of transverse rumble strips.

Since most rumble strips are installed at rural intersections
with relatively low volumes and few crashes, statistically significant results
require a large sample of intersections with long before-and-after periods,
especially since the reduction appears to be in severe injury crashes only. The
researchers note that further study on this topic should collect data from
other States that have implemented transverse rumble strips and examine the
effect on other crash types, such as run-off-road and sideswipe crashes at or
near intersections. Additional research should also investigate the
effectiveness of this treatment under a variety of conditions, including the
number of driveways, nature of the surrounding development and roadside
hazards, and sight distance.